EP4098802A1 - Geotechnical method and geotechnical arrangement - Google Patents

Abstract

The invention relates to a geotechnical method for the controlled shielding of a ground pressure on a building structure to be relieved in a ground to be stabilized, characterized by the steps:- Introducing profiles into the ground to be stabilized essentially perpendicular to the direction of the ground pressure to be shielded, the profiles being eccentrically arranged tendons can be prestressed,- tightening the tendons, whereby the profiles are bent against the ground pressure,- detection of a transverse force occurring at at least one end of the profile on which the profile is mounted, as a measure of the shielding achieved.Further, the invention relates a geotechnical arrangement resulting from the execution of the method.

Description

The invention relates to a geotechnical method for controlled shielding of a ground pressure on a building structure to be relieved in a ground to be stabilized. The invention also relates to a geotechnical arrangement that is created when the method is carried out.

Profiles that can be prestressed eccentrically are known in construction engineering. In this case, profile means, for example, a double-T steel girder, a steel tube, a reinforced concrete pole (with a round or square cross-section). Profiles that can be pretensioned eccentrically have one or more tensioning elements arranged on one side eccentrically to their central longitudinal axis, which are guided, for example, in a cladding tube. Common prestressing methods from solid construction are, for example, the bondless prestressing, which is used for reinforced concrete piles. The cladding tubes do not have to be pressed, which means that the prestressing cables have significantly smaller diameters and can therefore be used for relatively slim profiles. Furthermore, with this type of prestressing, there are hardly any stress changes in the prestressing steel (tendon) due to external loads because there is no bond. The process can be made more sustainable thanks to the bondless bracing. It can be restressed if, over time, concrete creep/shrinkage or stress cable relaxation reduces the stressing force and thus the deformation and shielding. In contrast, bonded prestressing can be used for reinforced concrete beams, which enables a force-locked bond between the tendon and the concrete.

Profiles that can be eccentrically prestressed in this way are known in solid construction, for example for bridges, but not yet for a geotechnical method for controlled shielding of ground pressure.

To stabilize a quay wall, it is known to place a so-called attachment on the water side in front of the quay wall to be rehabilitated. However, a projection undesirably changes the geometry of the harbor basin and is also technically complex with regard to the required back anchoring. Furthermore, it is known to introduce a non-prestressed pile wall on the land side of the existing quay wall to be protected, accepting an additional deformation or only arithmetically acting in the limit state, which, however, means only a limited relief for the existing quay wall. It is also possible to completely dismantle an endangered quay wall and replace it with a new building, which is logistically complex and very expensive.

From the KR 10 2 082 333 B1 is an eccentrically prestressed H-profile for the direct protection of terrain changes, in particular an excavation, in which the H-profile is introduced, for example by drilling into the untreated soil, the H-profile used is eccentrically braced and then the excavation pit is excavated to create the terrain change becomes. After completion of the building structure created in the excavation pit, the H-pile is relaxed by releasing the tension and can then be removed without any problems.

From the JP H05-54 630 U an earth retaining wall made of profiles that can be coupled to one another is known, with each profile being eccentrically prestressable in order to be able to better absorb the ground pressure occurring at a terrain change (excavation pit). The lower end of the profile is anchored below the excavation in the deeper soil and the upper end and, if necessary, secured in between by appropriate anchors.

Furthermore, in the JP H11-50 446A described a sheet piling element which has an eccentric bracing on the side of the ground pressure to be shielded. This is to prevent the sheet pile wall from leaning excessively outwards with its free upper end without additional anchoring in the deeper subsoil.

Although eccentrically tensionable profiles are described in these three aforementioned documents, these serve to increase the rigidity of the support wall formed in each case and thus to reduce deformations.

The object of the invention is to specify a method and an arrangement with which the ground pressure is shielded from a building structure to be relieved.

This problem is solved with the geotechnical method according to claim 1. The tightening of the tendons of the corresponding eccentrically prestressed profiles leads to a targeted and controllable deflection of the profiles or piles against the direction of the acting earth pressure. This creates an earth pressure vault between the eccentrically prestressed profiles in the ground. The profiles (piles) carry the loads over the bend to their two supported ends. To record the transverse forces acting at these ends, it is sufficient to record them at at least one end of the profile and to use them as a measure of the (controlled) shielding achieved.

Furthermore, this object is achieved with the geotechnical arrangement according to claim 9. Due to the fact that parallel to the building structure to be relieved on the side of the soil to be stabilized, a series of prestressable profiles are arranged in the ground essentially perpendicularly to the direction of the ground pressure to be shielded, after eccentric prestressing and bending of the profiles between adjacent profiles an earth pressure vault is created in the soil to be stabilized , which derives the critical soil pressure on the profiles and their storage in the deeper subsoil, i.e. relieves the building structure to be protected.

When the tensioning of the tendons is terminated and a specified value for the resulting transverse force is measured on the relevant profile, a characterizable earth pressure vault is formed, which demonstrably leads to the desired shielding of the soil pressure.

If the transverse force is checked continuously or at specified time intervals, it is possible to monitor the shielding effect achieved.

In a further development, the tendons can be re-tensioned if the transverse force that occurs on the relevant profile falls below a specified lower limit value. It is thus possible, in the event of any relief of the tendons (as a result of creep/shrinkage or relaxation), to readjust the required deflection by restressing the eccentrically prestressed profiles.

If the eccentrically arranged tendon is guided in a curved profile, additional deflection forces can be mobilized in the profile due to the curved tendon guide in the longitudinal direction of the profile, which enables greater deformation of the profile against the direction of the acting soil pressure. Due to the curved guidance of the tendon and its prestressing in the profile, a virtually infinite number of support points are created on the profile, which lead to an equalization of the acting deflection forces over the entire length of the profile and thus to a strong deformation of the profile, whereby a Earth pressure vault forms, which also leads to the preferred geotechnical arrangement.

This geotechnical method can be used in particular to stabilize a change in terrain. Horizontally or diagonally arranged, eccentrically prestressable profiles are also conceivable, however, which can absorb an overlay pressure (that is to say ground pressure) in a corresponding manner.

With regard to the geotechnical arrangement, the building structure to be relieved is a change in terrain, an embankment, a retaining wall or a quay wall.

In the case of a building structure to be relieved in the form of a change in terrain, a retaining wall or a quay wall, the row of prestressable profiles is parallel to the building structure and essentially perpendicular to the ground to be stabilized introduced, with the lower ends of the profiles being fixed in the ground below the building structure to be relieved and the upper ends of the profiles being fixed by means of load-bearing anchoring. Correspondingly, the excessive soil pressure is channeled through the earth pressure vaults that form between the prestressed profiles into the profiles and from there via the fixed bearing and load-bearing anchorage into the deeper subsoil, i.e. the retaining wall or quay wall is relieved so that it is permanently stable again. The shielded earth pressure can be measured, especially at the upper support, and regulated by the prestressing in such a way that the existing building structure is sufficiently relieved.

In particular, this geotechnical method or arrangement can be used to stabilize a quay wall with a support grid braced diagonally into the deeper subsoil, with the eccentrically prestressable profiles being introduced into the ground on the land side of this quay wall essentially parallel to it, with an upper end of each profile being anchored in the support grid and then the profiles are bent in the direction of the soil pressure by tightening the tendons.

What is special about this is that the earth pressure is transferred from the actual quay wall by means of a row of piles arranged behind the quay wall by forming earth pressure vaults. However, this requires ground movement, which usually does not occur or can be avoided. Due to the profiles or piles that can be eccentrically prestressed, the prestressing leads to a targeted and controllable deflection of the piles (profiles) in the direction of the acting earth pressure. Earth pressure arches are thus formed between the eccentrically prestressed profiles in the ground. The piles (profiles) transfer the loads via bending to the upper bearing, in the case of the embankment via the girder grid, and to the deeper subsoil. In order not to additionally stress the sheet piling from the mobilized earth resistance in the foot area of the piles, the eccentrically prestressed piles must be driven deep enough into the embed soil. Each profile is therefore preferably integrated into the ground with its lower end as deeper as possible than the existing quay wall.

The shielded earth pressure can be measured at the upper support and regulated by prestressing so that the existing quay wall is relieved.

The procedure for controlled earth pressure shielding is therefore as follows:
After the profile has been inserted and connected to the girder grid, the tensioning process begins. The prestress induces an eccentric normal force stress in the component, which causes a bending stress and thus the deflection of the profile. With a curved tendon guide in the profile, additional deflection forces are mobilized, which favor a greater horizontal deformation of the profile against the direction of the acting soil pressure. The controlled deformation mobilizes an earth pressure vault between the individual piles, which leads to a reduction in the earth pressure load on the existing quay wall (sheet piling). To assess the relief effect, the deformation of the profile (e.g. with chain inclinometers), the mobilized earth pressure in front of the profile and the bearing force (shear force) resulting from the horizontal load, which is introduced into the girder grid at the pile head, are measured with continuous monitoring. If the load-relieving effect is sufficient, the stressing process can be terminated and either the duct grouted with mortar (bonded prestressing) or the tendons are wedged on the pile head (unbonded prestressing).

In addition to being used to strengthen existing quay walls, this method and arrangement can also be used directly when planning new quay walls in order to mobilize the controlled earth pressure if necessary to be carried out and the sheet pile wall relieved. For this purpose, the first row of piles can consist directly of eccentrically prestressed profiles that are inserted into the ground and connected to the girder grid.

Fig. 1 a

einen Querschnitt durch eine Kaimauer mit ergänzenden, vorspannbaren Profilen,

Fig. 1 b

eine schematische Draufsicht auf die Profilrehe,

Fig. 2 a, b, c, d

beispielhaft verschiedene Profile im Querschnitt mit exzentrisch angeordneten Spanngliedern und

Fig. 3

eine alternative Ausführungsform eines Profils mit in Längsrichtung gekrümmt angeordnetem Spannglied.

Exemplary embodiments of the invention are described in detail below with reference to the accompanying figures. In it shows

1a

a cross section through a quay wall with supplementary, prestressable profiles,

Figure 1b

a schematic plan view of the profile deer,

Fig. 2a,b,c,d

Examples of different profiles in cross-section with eccentrically arranged tendons and

3

an alternative embodiment of a profile with longitudinally curved tendon arranged.

In 1 a quay wall is shown in cross-section as a building structure to be relieved. The quay wall 1 has a sheet piling 10 forming the change in terrain between the ground B and the body of water W of the harbor basin. The sheet pile wall 10 is introduced into the deeper subsoil U. At the upper end of the sheet pile wall 10, a support grid 11 is placed, which is optionally anchored in the ground B with anchors. Furthermore, at the head of the sheet pile wall 10 or the head of the girder grid 11, an anchoring 12 is provided which connects diagonally through the ground B into the deeper subsoil U and is intended to conduct soil and traffic loads from the quay wall into the subsoil. If the quay wall 1 can no longer safely absorb the existing soil pressure of soil B, the geotechnical method and arrangement described here for the controlled shielding of a soil pressure on a building structure to be relieved, namely quay wall 1 in this case, is ideal for efficient and cost-effective rehabilitation. In this case, on the land side of this quay wall 1, essentially parallel to the sheet piling 10, profiles 2 are cut into the ground B in one introduced spaced array. The profiles tie in deeper than the quay wall to be stabilized. The row of piles thus created parallel to the quay wall 1 is supported with its lower ends of the profiles 2 in the deeper subsoil U and at the upper end in the girder grid 11 of the existing quay wall 1 . The storage of the upper end of the respective profiles 2 is carried out by load application via the girder grid 11 and the anchoring 12 also in the deeper subsoil U.

The profiles 2 introduced into the subsoil have an eccentrically arranged clamping element 21 with which the profiles can be prestressed. Examples of such prestressable profiles are in 2 shown. 2 a shows an I-beam 2' with two tendons 21 arranged eccentrically on a flank of the I-profile, Figure 2b a round tube 2" with an eccentrically arranged clamping element 21, Fig. 2c a round reinforced concrete profile 2 ‴ with eccentrically arranged tendon 21 and Fig. 2d a square reinforced concrete pile 2"" with an eccentrically arranged tendon 21.

In an alternative embodiment, in 3 a profile is equipped with a tensioning element 21 arranged in the longitudinal direction of the profile, the tensioning element 21 being arranged in the profile curved over the longitudinal direction of the profile. where is in 3 the profile 2 is shown in a side view, with the ground B to be stabilized lying on the right in the plane of the drawing, which generates excessive ground pressure for a building structure lying to the left of the profile 2 (not shown here). In this exemplary embodiment, the tensioning element 21 is fastened in the profile 2 in a curved manner over the longitudinal direction of the profile, so that when the tensioning element 21 is tightened, the normal forces acting in the direction of the tensioning element 21, which in 3 are symbolized as two arrows oriented in the longitudinal direction of the tendon, mobilize deflection forces, which create a virtually infinite number of support points on the profile due to the uniform curvature of the tendon 21, whereby a uniform deflection force over the entire longitudinal direction of the profile against the direction of the acting soil pressure from the soil to be stabilized B works. This is schematic in 3 through the represented by regular arrows in the left rectangle. These symbolize the uniform deflection forces produced by the curved guidance of the tendon 21 and the tightening of the tendon 21 . These deflection forces acting over the entire longitudinal direction of the profile 2 produce a strong deformation of the profile (bending) in the direction of the soil B to be supported, whereby an earth pressure vault is formed in the soil B to be supported, which absorbs the excessive earth pressure from the plane of the drawing 3 left building structure (not shown here) shields and on the storage of the profile 2 at the bottom and at the top end (via the corresponding anchorage 12) in the deeper subsoil U incorporates.

In general, when tightening the tendon 21 according to eccentric arrangement. Fig. 2 a to d and/or by the longitudinally curved arrangement of the tendon 21, as in 3 , a deformation of the profile against the direction of the acting soil pressure is achieved. this is in Figure 1b as supervision of the geotechnical arrangement acc. 1 a with im in Figure 1b represented by the small arrow and hatching. After the profiles 2 have been prestressed, they curve as in 1 a dashed and shown with a small arrow against the ground pressure. Due to this bending of the profiles 2 and between the profiles 2 arranged at a distance from one another, corresponding soil pressure vaults are formed, which absorb the soil pressure in the plane spanned by the row of piles and conduct it via the profiles and their storage at the upper and lower ends into the deep subsoil U. Correspondingly, the sheet pile wall 10 of the quay wall 1 is actively relieved.

In order to verify a measure of the shielding of the ground pressure achieved by the newly introduced row of piles, the transverse force occurring at at least one end of the profile, preferably at the upper end of the profile at the bearing point in the girder grid 11, is measured. The lateral force determined is a direct measure of the relief of the existing quay wall.

reference list

1

building structure, quay wall

10

Retaining wall

11

girder grid

12

anchoring

2, 2', 2", 2‴, 2""

profile, post

21

tendon

B

floor

W

water body

u

deep underground

Claims (12)

Geotechnical method for the controlled shielding of a ground pressure on a building structure to be relieved in a ground to be stabilized, characterized by the steps: - Insertion of profiles in the ground to be stabilized essentially perpendicular to the direction of the ground pressure to be shielded, whereby the profiles can be prestressed by means of eccentrically arranged tendons, - tensioning of the tendons, whereby the profiles are bent against the ground pressure, - Detection of a transverse force arising at at least one end of the profile on which the profile is mounted, as a measure of the shielding achieved. Geotechnical method according to Claim 1, characterized in that the tensioning of the tendons is terminated when a predetermined value for the transverse force produced is measured on the relevant profile. Geotechnical method according to Claim 1 or 2, characterized in that the transverse force is measured continuously or at fixed time intervals. Geotechnical method according to Claim 3, characterized in that the tendons are restressed when a predetermined lower limit value for the transverse force occurring on the relevant profile is not reached. Geotechnical method according to one of the preceding claims, characterized in that the eccentrically arranged tendon is guided in a curved profile. Geotechnical method according to Claim 1, 2, 3 or 4 for stabilizing a quay wall with a support grid braced diagonally into the deeper subsoil, characterized in that the eccentrically prestressable profiles are introduced into the ground on the land side of this quay wall essentially parallel thereto, with an upper end of each Profile is anchored in the girder grid, and then the profiles are bent by tightening the tendons against the ground pressure. Geotechnical method according to claim 6, characterized in that the transverse forces acting between the grid and each profile are measured. Geotechnical method according to Claim 6 or 7, characterized in that the lower end of each profile is embedded in the ground deeper than the existing quay wall. Geotechnical arrangement for the controlled shielding of a ground pressure on a building structure to be relieved in a soil to be stabilized, characterized in that parallel to the building structure to be relieved on the side of the soil to be stabilized, a row of profiles that can be prestressed by means of eccentrically arranged tendons is laid in the ground essentially perpendicularly to the direction of the ground pressure to be shielded are arranged, with eccentric prestressing and bending of the profiles between adjacent profiles each forming an earth pressure vault in the ground to be stabilized. Geotechnical arrangement according to Claim 9, characterized in that the building structure to be relieved is a change in terrain, an embankment or a retaining wall, a quay wall. Geotechnical arrangement according to Claim 10, characterized in that in the case of a building structure to be relieved in the form of a retaining wall or a quay wall, the row of prestressable profiles is introduced parallel to the building structure and essentially perpendicularly in the ground to be stabilized, the lower ends of the profiles being below the to be relieved building structure are firmly stored in the ground and the upper ends of the profiles are firmly stored by means of load-bearing anchorage. Geotechnical arrangement according to one of Claims 9 to 11, characterized in that the tendon arranged eccentrically in the profile is curved in the profile.

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